Impairments in wireless channels can cause bit errors that result in packet losses and adversely impact TCP throughput. Presence of interference (both in band and out of band) adds to the problem because it results in a higher error rate and diminished throughput. In such environments, intelligent schemes are required at several layers to mitigate the negative effects of these losses. ARQ mechanisms are widely used in wireless communication networks as a method to alleviate these issues, ensure data integrity, improve reliability, and to some extent guarantee in-order delivery of packets at the receiver.
When implemented at the link layer, in conjunction with Fragmentation and Re-assembly techniques, along with a sliding window approach as disclosed in US Provisional Application Ser. No. 61/735,264, “Hybrid ARQ System Using A Sliding Purge Window For Wireless Networks” filed Dec. 10, 2012 and incorporated herein, the transmitter usually can send multiple IP packets that are fragmented into several media access control (MAC) layer fragments. These fragments can be sent out of order and are then re-assembled at the receiver. This reassembly requires a MAC layer fragment identifier and sequence number. When the wireless channel degrades, as in a deep fade, the losses can continue for extended periods of time and within a second the receiver and transmitter can get out of sync because the acknowledgment messages (ACKs) are lost. What is proposed in this disclosure is a novel scheme to alleviate this problem by having the transmitter opportunistically piggy-back a snapshot of the transmitter's transmit/send window in data frames. When the receiver receives this snapshot the receiver can compare it with its receive window and if a mismatch is detected, whereby the transmitter has moved on to the next packet, the receiver can now also sync up quicker and not wait for the regular timeout to progress ahead.